Documentation 2026-06-18 00:57 UTC to 2026-06-19 05:59 UTC

147| Parameter | Type | Description |147| Parameter | Type | Description |

148|-----------|------|-------------|148|-----------|------|-------------|

149| `instructions` | string | System prompt |149| `instructions` | string | System prompt |

150| `reasoning_effort` | `"high"` | `"none"` | optional | Controls whether the model uses reasoning. Defaults to `"high"`. Supported only with `grok-voice-latest` and `grok-voice-think-fast-1.0`. |150| `reasoning.effort` | `"high"` | `"none"` | optional | Controls whether the model uses reasoning. Defaults to `"high"`. Supported only with `grok-voice-latest` and `grok-voice-think-fast-1.0`. |

151| `voice` | string | Voice selection: `eve`, `ara`, `rex`, `sal`, `leo`, or a [custom voice ID](/developers/model-capabilities/audio/custom-voices) (see [Available Voices](#available-voices)) |151| `voice` | string | Voice selection: `eve`, `ara`, `rex`, `sal`, `leo`, or a [custom voice ID](/developers/model-capabilities/audio/custom-voices) (see [Available Voices](#available-voices)) |

152| `tools` | array | Tools available to the voice agent. Supports `file_search`, `web_search`, `x_search`, `mcp`, and `function` types. See [Using Tools](#using-tools-with-grok-voice-agent-api). |152| `tools` | array | Tools available to the voice agent. Supports `file_search`, `web_search`, `x_search`, `mcp`, and `function` types. See [Using Tools](#using-tools-with-grok-voice-agent-api). |

153| `turn_detection.type` | string | null | `"server_vad"` for automatic detection, `null` for manual text turns |153| `turn_detection.type` | string | null | `"server_vad"` for automatic detection, `null` for manual text turns |

1558 1558 

1559* **Simplify your system prompt.** The model is significantly more capable, so your prompt should be much shorter. Ask Grok to generalize your existing system prompt rather than porting it verbatim.1559* **Simplify your system prompt.** The model is significantly more capable, so your prompt should be much shorter. Ask Grok to generalize your existing system prompt rather than porting it verbatim.

1560* **Remove workaround prompting.** Prompt hacks and edge-case fixes needed for GPT models are unnecessary. Strip out instructions added solely to patch bugs or limitations of the previous model.1560* **Remove workaround prompting.** Prompt hacks and edge-case fixes needed for GPT models are unnecessary. Strip out instructions added solely to patch bugs or limitations of the previous model.

1561* **Reasoning is enabled by default.** The default `reasoning_effort` is `"high"` for complex multi-step instructions, nuanced tone, and ambiguous queries. Set it to `"none"` to disable reasoning.1561* **Reasoning is enabled by default.** The default `reasoning.effort` is `"high"` for complex multi-step instructions, nuanced tone, and ambiguous queries. Set it to `"none"` to disable reasoning.

1562 1562 

1563#### Deprecated model1563#### Deprecated model

1564 1564 

38| grok-4.20-0309-non-reasoning | T0: 1.8K, T1: 2.4K, T2: 3.6K, T3: 6K, T4: 10K | T0: 10M, T1: 15M, T2: 25M, T3: 45M, T4: 85M |38| grok-4.20-0309-non-reasoning | T0: 1.8K, T1: 2.4K, T2: 3.6K, T3: 6K, T4: 10K | T0: 10M, T1: 15M, T2: 25M, T3: 45M, T4: 85M |

39| grok-build-0.1 | T0: 1.8K, T1: 2.4K, T2: 3.6K, T3: 6K, T4: 10K | T0: 10M, T1: 15M, T2: 25M, T3: 45M, T4: 85M |39| grok-build-0.1 | T0: 1.8K, T1: 2.4K, T2: 3.6K, T3: 6K, T4: 10K | T0: 10M, T1: 15M, T2: 25M, T3: 45M, T4: 85M |

40| grok-4.20-multi-agent-0309 | T0: 450, T1: 600, T2: 900, T3: 1.5K, T4: 2.7K | T0: 2.5M, T1: 3.7M, T2: 6.2M, T3: 11M, T4: 21M |40| grok-4.20-multi-agent-0309 | T0: 450, T1: 600, T2: 900, T3: 1.5K, T4: 2.7K | T0: 2.5M, T1: 3.7M, T2: 6.2M, T3: 11M, T4: 21M |

41| grok-imagine-image | 300 | 0 |

42| grok-imagine-image-quality | 300 | 0 |41| grok-imagine-image-quality | 300 | 0 |

42| grok-imagine-image | 300 | 0 |

43| grok-imagine-video | 70 | 0 |43| grok-imagine-video | 70 | 0 |

44| grok-imagine-video-1.5 | 60 | 0 |44| grok-imagine-video-1.5 | 60 | 0 |

45 45 

16 16 

17 * `model` ("grok-voice-latest" | "grok-voice-think-fast-1.0" | "grok-voice-fast-1.0") — Model to use for the session. Use grok-voice-latest for the best experience.17 * `model` ("grok-voice-latest" | "grok-voice-think-fast-1.0" | "grok-voice-fast-1.0") — Model to use for the session. Use grok-voice-latest for the best experience.

18 18 

19 * `reasoning_effort` ("high" | "none") — Controls whether the model uses reasoning. Defaults to \`high\`. Supported only with \`grok-voice-latest\` and \`grok-voice-think-fast-1.0\`.19 * `reasoning` (object) — Reasoning settings for models that support them.

20 

21 * `effort` ("high" | "none") — Controls whether the model uses reasoning. Defaults to \`high\`. Supported only with \`grok-voice-latest\` and \`grok-voice-think-fast-1.0\`.

20 22 

21### Response Body23### Response Body

22 24 

100 102 

101* `model` (string, optional, default: grok-voice-latest) — Model to use for the session. Use grok-voice-latest for the best experience.103* `model` (string, optional, default: grok-voice-latest) — Model to use for the session. Use grok-voice-latest for the best experience.

102 104 

103* `reasoning_effort` (string, optional, default: high) — Controls whether the model uses reasoning. Defaults to \`high\`. Supported only with grok-voice-latest and grok-voice-think-fast-1.0.105* `reasoning.effort` (string, optional, default: high) — Controls whether the model uses reasoning. Defaults to \`high\`. Supported only with grok-voice-latest and grok-voice-think-fast-1.0.

104 106 

105### Client Messages107### Client Messages

106 108